Advances in computational photography have enabled richer visualizations of digitized real world scenes, when compared with traditional media items, such as photographs. Relightable media items, referred to here as photographs, are one such technique that can supplement the visual experience provided by a conventional digital photograph. This technology allows users to interact with a photograph by changing the incident illumination of the scene, or alternatively allows the photograph to adapt according to the current illumination scenario in the environment where the photograph is displayed. Relightable photographs are thus alternatives to traditional photographs, as they provide a richer viewing experience.
More than a decade ago, the lighting-sensitive display was first proposed as a medium for displaying photographs that respond to the viewing environment by dynamically changing their incident illumination. Such relightable photographs are created by acquiring the scene's reflected field, so that the scene can be rendered under novel illumination conditions. Acquiring the reflectance function of a real-world scene is called inverse rendering, and a large number of acquisition frameworks focus on fast and accurate acquisition of the reflectance function. However, the complexity and the scale of most of the existing acquisition frameworks prevent widescale use beyond specialized studios.
The two existing frameworks for scene relighting involve either acquiring the parametric form of per-pixel reflectance functions or through image based relighting. Object relighting tries to recreate the appearance of a pictured scene or object under new illumination. Several acquisition setups that involve complex light stages with fixed or movable light sources mounted on robotic arms exist and thus are limited in their accessibility. Polynomial texture mapping is a technique that uses a glossy black sphere to determine the illumination angle, and models per-pixel reflectance using biquadratic polynomials. Pocket reflectometry is a second portable method where a reference bidirectional reflective distribution function (BRDF) chart is used in combination with a handheld light source to acquire parametric surface reflectance.
It is an object of the present invention to overcome the problems related to the existing techniques for relighting a media item and thus to provide a media item relighting solution which is simple, yet reliable and efficient, and which is easily accessible to a large number of users.